For many years industry, and particularly the transportation industry, has been concerned with designing compositions that function to provide sealing, baffling, vibrational and acoustical damping to articles of manufacture such as transportation vehicles (e.g. automotive vehicles). Cavities resulting from design and assembly of transportation vehicles allow the movement of such things as sound, water and debris to the detriment of the vehicle and passengers. Numerous solutions to the sealing of such cavities have been proposed. One such solution is the attachment of preformed, heat activatable foamable parts to the inside or near vicinity of the cavities. Typically these parts rely on an external heat source to activate a foaming agent inside the preformed part, causing it to expand and completely, or near completely, and fill the targeted cavity. In automotive applications, a preformed sealant is installed during body assembly, where the assembled body is then dipped in an e-coat bath and guided through an oven to dry and cure the corrosion resistant e-coat coating. In this example, the preformed sealant has been designed to expand and cure when exposed to the e-coat oven heat. One design difficulty in these automotive applications arises from differences in oven temperature (between ovens or within an oven) and differences in heat exposure time. It would therefore be desirable for sealant compositions utilized in such applications to exhibit one or more properties that allow the compositions to expand consistently and uniformly over a wider range of bake times and temperatures.
Phenolic resin compositions themselves are well known and used as resinous based materials for heat stable parts in a wide range of industries. For example, in U.S. Pat. No. 5,162,428, novolac and resole type phenolic resins are combined to make molding materials with high strength and good heat and dimensional stability for the molding of automotive mechanical parts. U.S. Pat. No. 6,838,509 provides for phenolic resin composite materials composed of a phenolic resin, a filler and an organized clay layer which provides heat resistance and mechanical strength for components in the automotive and aerospace industries. However, phenolic resin compositions have not been traditionally used as foamed sealers or as stabilizers of foam sealers such as those described by the present invention.
Phenolic resins and phenolic resin compositions may be foamed through the addition of chemical blowing agents such as those described in U.S. Pat. No. 4,423,163 and International Publication WO 98/50458. However, such uses have not previously been described to include the use of phenolic resins to stabilize polyolefin based foam compositions at high temperatures.
Phenolic resins are also known to chemically crosslink polyolefin-based elastomers containing unsaturation. For example, in U.S. Pat. No. 2,701,895 the curing of polyisobutylene thermoset elastomer compounds is disclosed using a phenolic type resin. Phenolic resins are also used to crosslink the unsaturated portion of blends of saturated and unsaturated polyolefins, leading to the formation of thermoplastic elastomers or thermoplastic vulcanizates as described by U.S. Pat. Nos. 4,311,628 and 5,977,271. In either case of phenolic cured thermoset elastomers or thermoplastic elastomers, they may be foamed. However, the function of the phenolic resin is as the primary crosslinking agent.
It is thus desirable for sealant compositions utilized in applications with variable temperatures to exhibit one or more properties that allow the compositions to expand consistently and uniformly over a wide range of bake times and temperatures. Additionally, it is typically desirable for these compositions to exhibit one or more properties that allow the compositions to be more functional and more easily processed. The present invention meets some or all of the above needs by providing for the addition of a phenolic resin to form a more heat stable soft polymer expandable foam composition for use in such applications.